Method for removing metal oxides using cleaning plasma

Abstract

Embodiments of the present disclosure relate to methods of removing metal oxides from a substrate surface by exposing the substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H2) and oxygen (O2). In some embodiments, the substrate surface has at least one feature on the substrate surface, the at least one feature defining a trench having a top surface, a bottom surface, and two opposing sidewalls. The unbiased cleaning plasma includes oxygen (O2) in a range of 1% to 20% by molecule and hydrogen (H2) greater than or equal to 80% by molecule. An unbiased cleaning plasma removes substantially all of the metal oxides, such as molybdenum oxide (MoOx), ruthenium oxide (RuOx) or tungsten oxide (WOx), from the substrate surface and the top, bottom and two opposing sidewalls of the trench without damaging the dielectric and / or critical dimension (CD) / profile of the structure.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to methods for removing metal oxides from a substrate surface. In particular, embodiments of the present disclosure relate to methods for removing metal oxides by using an unbiased cleaning plasma. Background Art

[0002] Integrated circuits can be fabricated through processes that create patterned material layers on a substrate. Creating patterned materials on a substrate requires controlled methods for removing exposed materials. Chemical etching is used for a variety of purposes, including transferring a pattern in a photoresist into a underlying layer, thinning a layer, or thinning the lateral dimensions of features already present on a surface. Sometimes, an etching process that etches one material faster than another must be available to facilitate, for example, a pattern transfer process.

[0003] A substrate being introduced typically has residues from previous processing, natural oxide formation on metals, and etching residues from via / trench hole formation. To improve the process performance of metal filling, such as low line resistance, high yield, and high reliability, any residues and / or natural oxides must be removed. Separate remote plasmas and direct plasmas cannot effectively remove residues and natural oxides inside structures. Remote plasma radicals cannot reach the structure trenches sufficiently due to their lifetime, and direct plasmas cannot clean the sidewalls of structures due to directionality.

[0004] Natural oxides such as tungsten oxide (WO x ) are formed due to etching vias / trenches and vacuum breaks. Therefore, a pre-clean process is needed to clean natural oxides such as tungsten oxide (WO x ) to minimize the resistance capacitance ("resistivity" or "resistance") in an integrated circuit. Resistivity is an inherent property of a material and is a measure of the resistance of the material to the movement of charge through the material. The resistivity of a material affects the electrical operation of an integrated circuit.

[0005] Current pre-clean processes include exposing the substrate to a plasma of argon (Ar) and hydrogen (H 2 ) to remove natural oxides. These pre-clean processes are performed with an external bias present on the substrate surface, which may damage the dielectric and critical dimension (CD) / profile of the structure.

[0006] Accordingly, there is a need in the art for improved processes for etching (cleaning) materials and structures on a semiconductor substrate without damaging the dielectric and / or critical dimension (CD) / profile of the structure. Summary of the Invention

[0007] One or more embodiments relate to a method of removing metal oxides from a substrate surface. The method includes exposing the substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) to remove the metal oxides and form a clean metal surface. The unbiased cleaning plasma comprises from 1% to 20% by molecules of oxygen (O 2 ).

[0008] Additional embodiments are directed to a processing method that includes exposing a substrate surface having at least one feature thereon to a pre-cleaning process. The at least one feature defines a trench having a top surface, a bottom surface, and two opposing sidewalls. Metal oxides are present on each of the top surface, the bottom surface, and the two opposing sidewalls. The pre-cleaning process includes exposing the top surface, the bottom surface, and the two opposing sidewalls to an unbiased cleaning plasma to remove the metal oxides and thereby form a clean metal surface, the unbiased cleaning plasma consisting essentially of a mixture of hydrogen (H 2 ) and from 1% to 20% by molecules of oxygen (O 2 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To enable a detailed understanding of the above-described features of the present disclosure, reference may be made to the embodiments in which the present disclosure briefly summarized above is described in more detail, some of which are illustrated in the drawings. It should be noted, however, that the drawings only illustrate typical embodiments of the present disclosure and should not be considered as limiting its scope, as the present disclosure may admit other equivalent embodiments. The embodiments described herein are shown by way of example and not limitation in the drawings, in which like reference numerals represent like elements.

[0010] Figure 1 A process flow diagram of a method according to one or more embodiments of the present disclosure is shown;

[0011] Figure 2 A process flow diagram of a processing method according to one or more embodiments of the present disclosure is shown;

[0012] Figure 3A A cross-sectional schematic view of a feature on a substrate according to one or more embodiments of the present disclosure is shown;

[0013] Figure 3B A cross-sectional schematic view of the feature having a clean metal surface after exposure to an unbiased cleaning plasma according to one or more embodiments of the present disclosure is shown; Figure 3A shown;

[0014] Figure 3Cshows a cross-sectional schematic view of a metal film formed on a cleaned metal surface according to one or more embodiments of the present disclosure; and Figure 3B a cross-sectional schematic view of a metal film formed on the cleaned metal surface shown; and

[0015] Figure 3D shows a cross-sectional schematic view of a metal film filling the features shown in Figure 3B the filling. DETAILED DESCRIPTION

[0016] Before describing several exemplary embodiments of the present disclosure, it should be understood that the present disclosure is not limited to the details of the structures or process steps set forth in the following description. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways.

[0017] As used herein, a "substrate" refers to any substrate on which film processing is performed during a process or any material surface formed on a substrate. For example, depending on the application, substrate surfaces on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon-doped silicon oxide, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials. Substrates include, but are not limited to, semiconductor wafers.

[0018] The substrate can be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal, and / or bake the substrate surface. In addition to performing film processing directly on the surface of the substrate itself, in the present disclosure, any of the disclosed film processing steps can also be performed on an underlying layer formed on the substrate, as disclosed in more detail below, and the term "substrate surface" is intended to include such underlying layers as referred to in context. Thus, for example, in the case where a film / layer or a portion of a film / layer has been deposited on a substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface.

[0019] As used herein, the term "substrate surface" refers to any substrate surface on which a layer can be formed. The substrate surface can have one or more features formed therein or thereon, one or more layers formed thereon, and combinations of the foregoing. The shape of the feature can be any suitable shape, including but not limited to peaks, trenches, and cylindrical vias. In this sense, the term "feature" refers to any intentionally present surface irregularity. Suitable examples of features include but are not limited to trenches having a top surface, two opposing sidewalls, and a bottom surface, peaks having a top extending upward from the surface and two sidewalls, and vias having sidewalls extending downward from a surface with a bottom. In some embodiments, the bottom of the via includes an open bottom defined or bounded by an underlying material (e.g., a dielectric material), which can also define the two sidewalls, or the underlying material of the bottom can be a conductor such as a metal (e.g., copper), which can be the same or different from the sidewall material.

[0020] The term "on" indicates direct contact between elements. The term "directly on" indicates direct contact between elements and the absence of an intervening element.

[0021] "Atomic layer deposition" or "cyclic deposition" as used herein refers to the sequential exposure of two or more reactive compounds to deposit a layer of material on a substrate surface. The substrate or a portion of the substrate is exposed to two or more reactive compounds introduced into the reaction zone of a processing chamber, respectively. In a time-domain ALD process, the exposure to each reactive compound is separated by a time delay to allow each compound to attach to and / or react on the substrate surface, followed by purging from the processing chamber. These reactive compounds are referred to as being sequentially exposed to the substrate. In a spatial ALD process, different portions of the substrate surface or the material on the substrate surface are simultaneously exposed to two or more reactive compounds such that any given point on the substrate is not substantially simultaneously exposed to more than one reactive compound. As used in this specification and the appended claims, those skilled in the art will understand that the term "substantially" in this context means that due to diffusion, a small portion of the substrate may be simultaneously exposed to multiple reactive gases, and the simultaneous exposure is not intentional.

[0022] In one aspect of a time-domain ALD process, a first reactive gas (i.e., a first precursor or compound A) is pulsed into the reaction zone and then undergoes a first time delay. Subsequently, a second precursor or compound B is pulsed into the reaction zone and then undergoes a second delay. During each time delay, a purge gas such as argon is introduced into the processing chamber to purge the reaction zone or otherwise remove any residual reactive compounds or reaction by-products from the reaction zone. Alternatively, the purge gas can flow continuously throughout the deposition process such that only the purge gas is flowing during the time delay between pulses of the reactive compounds. The reactive compounds are pulsed alternately until a desired film or film thickness is formed on the substrate surface. In either case, the ALD process of pulsing compound A, the purge gas, compound B, and the purge gas is one cycle. The cycle can start with compound A or compound B and continue in their respective cycle order until a film of a predetermined thickness is obtained.

[0023] In one embodiment of a spatial ALD process, a first reactive gas and a second reactive gas (e.g., nitrogen) are simultaneously delivered to the reaction zone but are separated by an inert gas curtain and / or a vacuum curtain. The substrate is moved relative to the gas delivery device such that any given point on the substrate is exposed to the first reactive gas and the second reactive gas.

[0024] In one or more embodiments, the film is conformally deposited on the surface. As used herein, the term "conformal" or "conformally" refers to a film that adheres to and uniformly covers the exposed surface and has a variation in thickness that is less than 5%, less than 2%, or less than 1% relative to the average thickness of the film. For example, a film that is 1000 angstroms thick may have a thickness variation of less than 10 angstroms. Such thickness and variation include at least the edges, corners, sides, and bottoms of grooves. For example, in various embodiments of the present disclosure, a conformal film deposited by ALD will provide coverage of substantially uniform thickness over the deposition area on a complex surface.

[0025] Embodiments of the present disclosure advantageously provide a method for removing metal oxides from a substrate surface in the absence of an external bias on the substrate surface. Advantageously, the present disclosure provides a process for etching (cleaning) materials and structures on a semiconductor substrate without damaging the dielectric and / or critical dimension (CD) / profile of the structure.

[0026] The inventors have surprisingly found that an unbiased cleaning plasma using a mixture containing hydrogen (H 2 ) and oxygen (O 2 ) can remove metal oxides from the substrate surface in the absence of an external bias on the substrate surface. Advantageously, in the absence of an external bias on the substrate surface, a mixture containing hydrogen (H 2 ) and oxygen (O 2An unbiased cleaning plasma of the mixture removed all or substantially all of the metal oxides from the substrate surface.

[0027] In some embodiments, when the unbiased cleaning plasma comprises from 1% to 20% by molecules of oxygen (O 2 ) and greater than or equal to 80% of hydrogen (H 2 ), a chemical vapor transport (CVT)-type reaction is observed. In a chemical vapor transport reaction, the deposited solid is non-volatile. For example, the non-volatile deposition compound can be a metal oxide such as molybdenum oxide (MoO x ), ruthenium oxide (RuO x ), or tungsten oxide (WO x ). Non-volatile solids such as molybdenum oxide (MoO x ), ruthenium oxide (RuO x ), or tungsten oxide (WO x ) volatilize in the presence of reactants such as a mixture of hydrogen (H 2 ) and oxygen (O 2 ) as described herein. Hydrogen (H 2 ) and oxygen (O 2 ) react with metal oxides such as molybdenum oxide (MoO x ), ruthenium oxide (RuO x ), or tungsten oxide (WO x ). The compounds formed by the reaction of a mixture of hydrogen (H 2 ) and oxygen (O 2 ) with metal oxides such as molybdenum oxide (MoO x ), ruthenium oxide (RuO x ), or tungsten oxide (WO x ) volatilize as metals such as molybdenum (Mo), ruthenium (Ru), or tungsten (W). Subsequently, the volatilized metal materials such as molybdenum (Mo), ruthenium (Ru), or tungsten (W) can be transported in gaseous form and deposited on the substrate as a metal film or crystal.

[0028] Other embodiments of the present disclosure are described through the accompanying drawings, which show a substrate surface, features formed on the substrate surface, and a process for removing metal oxides from the substrate surface and the feature surfaces according to one or more embodiments of the present disclosure. The processes shown are merely illustrative potential uses of the disclosed processes, and those skilled in the art will recognize that the disclosed processes are not limited to the applications shown.

[0029] Figure 1 A process flow diagram of method 100 according to one or more embodiments is shown. Figure 2A process flow diagram of a processing method 200 according to one or more embodiments is shown.

[0030] In operation 110, method 100 includes exposing a substrate surface to an unbiased cleaning plasma to form a clean metal surface. In some embodiments, method 100 consists essentially of exposing a substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) to remove metal oxides and thereby form a clean metal surface. In other embodiments, method 100 consists of exposing a substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) to remove metal oxides and thereby form a clean metal surface.

[0031] In some embodiments, the unbiased cleaning plasma includes a mixture of hydrogen (H 2 ) and oxygen (O 2 ). In some embodiments, the unbiased cleaning plasma includes a mixture of hydrogen (H * ) radicals and oxygen (O * ) radicals. In some embodiments, the unbiased cleaning plasma includes a mixture of hydrogen (H + ) ions and oxygen (O -2 ) ions. In some embodiments, the unbiased cleaning plasma includes one or more of hydrogen (H 2 ) / hydrogen (H * ) radicals / hydrogen (H + ) ions and oxygen (O 2 ) / oxygen (O * ) radicals / oxygen (O -2 ) ions, and any combination of the foregoing. In some embodiments, the unbiased cleaning plasma includes oxygen (O 2 ) in the range of 1% to 20% by molecules. In some embodiments, the mixture of hydrogen (H 2 ) and oxygen (O 2 ) includes greater than or equal to 80% hydrogen (H 2 ). In other embodiments, the mixture of hydrogen (H 2 ) and oxygen (O 2 ) includes greater than or equal to 90% hydrogen (H 2 ).

[0032] An unbiased cleaning plasma can be generated by any suitable plasma source known to those skilled in the art. In some embodiments, the unbiased cleaning plasma is generated by a plasma source selected from one or more of a capacitively coupled plasma (CCP) source, an inductively coupled plasma (ICP) source, a microwave plasma source, or a remote plasma source.

[0033] Neither a separate remote plasma nor a direct plasma can effectively remove residues and native oxides inside the structure. Remote plasma radicals cannot reach the structure trenches sufficiently due to their lifetime, and direct plasma cannot clean the sidewalls of the structure due to its directionality.

[0034] Advantageously, when the unbiased cleaning plasma contains oxygen (O 2 ) in the range of 1% to 20% by molecules and hydrogen (H 2 ) greater than or equal to 80%, a chemical vapor transport (CVT)-type reaction is observed, and volatile metal materials such as molybdenum (Mo), ruthenium (Ru), or tungsten (W) can be transported in gaseous form and deposited on the substrate as a metal film or crystal.

[0035] In some embodiments, the substrate surface is maintained at a temperature greater than or equal to 300°C. In some embodiments, the substrate surface is maintained at a temperature in the range of 300°C to 750°C, including all values and sub-ranges therebetween. The substrate surface can be maintained at a temperature in the range of 300°C to 750°C, including all values and sub-ranges therebetween, and the substrate surface is exposed to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) which advantageously forms a clean metal surface. The unbiased cleaning plasma has hydrogen (H 2 ) greater than or equal to 80%, or hydrogen (H 2 ) greater than or equal to 90%. For example, in some embodiments, when the mixture of hydrogen (H 2 ) and oxygen (O 2 ) contains hydrogen (H 2 ) greater than or equal to 90%, the substrate surface can be maintained at a temperature in the range of 300°C to less than or equal to 500°C. In some embodiments, when the mixture of hydrogen (H 2 ) and oxygen (O 2 ) contains hydrogen (H 2 ) greater than or equal to 80%, the substrate surface can be maintained at a temperature in the range of greater than or equal to 500°C to 750°C.

[0036] In some embodiments, method 100 is performed at a pressure less than or equal to 50 mTorr, including less than or equal to 40 mTorr, less than or equal to 30 mTorr, or less than or equal to 20 mTorr. In some embodiments, method 100 is performed at a pressure greater than or equal to 50 mTorr. In some embodiments, method 100 is performed at a pressure in the range from greater than or equal to 50 mTorr to less than or equal to 5 Torr, including all values and sub-ranges therebetween.

[0037] An unbiased cleaning plasma advantageously removes substantially all of the metal oxides from the substrate surface. As used in this context, "substantially all of the metal oxides" means less than about 5% of the total composition of the metal oxides remaining on the substrate surface after exposing the substrate surface to the unbiased cleaning plasma, including less than about 4%, less than about 3%, less than about 2%, less than about 1%, less than about 0.5%, and less than about 0.1%.

[0038] In some embodiments, method 100 advantageously includes exposing the substrate surface once to an unbiased cleaning plasma to remove all or substantially all of the metal oxides from the substrate surface in the absence of an external bias on the substrate surface.

[0039] In operation 120, method 100 optionally includes depositing a metal film on the cleaned metal surface. The metal film can include any metal known to those skilled in the art. In some embodiments, the metal film includes a transition metal. In some embodiments, the metal film includes one or more of molybdenum (Mo), ruthenium (Ru), or tungsten (W), or alloys thereof. In some embodiments, depositing the metal film on the cleaned metal surface includes one or more of atomic layer deposition (ALD), chemical vapor deposition (CVD), or pulsed CVD (pCVD). In some embodiments, the substrate surface is exposed to a first precursor and a second precursor simultaneously. In some embodiments, the substrate surface is exposed to the first precursor and the second precursor sequentially.

[0040] In some embodiments, depositing the metal film includes atomic layer deposition (ALD), which includes exposing the substrate surface to one or more cycles of a first precursor, a purge gas, a second precursor, and a purge gas.

[0041] In some embodiments, depositing a metal film includes a spatial ALD process in which a first reactive gas and a second reactive gas are simultaneously delivered to a reaction zone but separated by an inert gas curtain and / or a vacuum curtain. In some embodiments, depositing a metal film includes co-flowing the first reactive gas and the second reactive gas. In some embodiments, depositing a metal film includes chemical vapor deposition (CVD). In some embodiments, depositing a metal film includes pulsed chemical vapor deposition (pCVD) in which one or both reactants are pulsed into a processing chamber.

[0042] In some embodiments, method 100 consists essentially of: exposing a substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) to remove metal oxides, thereby forming a clean metal surface (operation 110), and depositing a metal film on the clean metal surface (operation 120). In other embodiments, method 100 consists of: exposing a substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) to remove metal oxides, thereby forming a clean metal surface (operation 110), and depositing a metal film on the clean metal surface (operation 120).

[0043] Some embodiments are directed to a processing method for removing metal oxides from a bottom surface of features formed on a substrate surface. In operation 210, processing method 200 optionally includes forming at least one feature on the substrate surface. The at least one feature can be formed by any process known to those skilled in the art. In some embodiments, the at least one feature defines a trench having a top surface, a bottom surface, and two opposing sidewalls, each of the top surface, the bottom surface, and the two opposing sidewalls having metal oxides.

[0044] In some embodiments, in operation 220, processing method 200 includes exposing the substrate surface having at least one feature to a pre-cleaning process. In some embodiments, the pre-cleaning process includes exposing the top surface, the bottom surface, and the two opposing sidewalls to an unbiased cleaning plasma to remove metal oxides, thereby forming a clean metal surface, the unbiased cleaning plasma consisting essentially of hydrogen (H 2 ) and oxygen (O 2 ) in a molecular range of 1% to 20%. In some embodiments, the mixture of hydrogen (H 2 ) and oxygen (O 2 ) includes greater than or equal to 80% hydrogen (H 2)。In other embodiments, the mixture of hydrogen (H 2 ) and oxygen (O 2 ) includes greater than or equal to 90% hydrogen (H 2 ).

[0045] In some embodiments, the substrate surface is maintained at a temperature greater than or equal to 300 °C. In some embodiments, the substrate surface is maintained at a temperature in the range of 300 °C to 750 °C, including all values and sub-ranges therebetween. The substrate surface can be maintained at a temperature in the range of 300 °C to 750 °C, including all values and sub-ranges therebetween, and exposing the substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) advantageously forms a clean metal surface, the mixture having greater than or equal to 80% hydrogen (H 2 ), or greater than or equal to 90% hydrogen (H 2 ). For example, in some embodiments, when the mixture of hydrogen (H 2 ) and oxygen (O 2 ) contains greater than or equal to 90% hydrogen (H 2 ), the substrate surface can be maintained at a temperature in the range of 300 °C to less than or equal to 500 °C. In some embodiments, when the mixture of hydrogen (H 2 ) and oxygen (O 2 ) contains greater than or equal to 80% hydrogen (H 2 ), the substrate surface can be maintained at a temperature in the range of greater than or equal to 500 °C to 750 °C.

[0046] In some embodiments, the processing method 200 is performed at a pressure less than or equal to 50 mTorr, including less than or equal to 40 mTorr, less than or equal to 30 mTorr, or less than or equal to 20 mTorr. In some embodiments, the processing method 200 is performed at a pressure greater than or equal to 50 mTorr. In some embodiments, the processing method 200 is performed in a pressure range from greater than or equal to 50 mTorr to less than or equal to 5 Torr, including all values and sub-ranges therebetween.

[0047] The unbiased cleaning plasma advantageously removes substantially all of the metal oxides from the substrate surface. As used in this sense, "substantially all of the metal oxides" means less than about 5% of the total composition of the metal oxides remaining on the substrate surface after exposing the substrate surface to the unbiased cleaning plasma, including less than about 4%, less than about 3%, less than about 2%, less than about 1%, less than about 0.5%, and less than about 0.1%.

[0048] In some embodiments, method 200 advantageously includes exposing the substrate surface to a pre-cleaning process a single time in the absence of an external bias on the substrate surface to remove all or substantially all of the metal oxide from the substrate surface.

[0049] In some embodiments, in operation 230, the processing method 200 optionally includes depositing a metal film on the cleaned metal surface. The metal film can include any metal known to those skilled in the art. In some embodiments, the metal film includes a transition metal. In some embodiments, the metal film includes one or more of molybdenum (Mo), ruthenium (Ru), or tungsten (W), or an alloy of any of the foregoing. In some embodiments, depositing the metal film on the cleaned metal surface includes one or more of atomic layer deposition (ALD), chemical vapor deposition (CVD), or pulsed CVD (pCVD). In some embodiments, the substrate surface is exposed to a first precursor and a second precursor simultaneously. In some embodiments, the substrate surface is exposed to the first precursor and the second precursor sequentially.

[0050] In some embodiments, the processing method 200 consists essentially of: forming at least one feature that includes a top surface, a bottom surface, and two opposing sidewalls (operation 210), each of the top surface, the bottom surface, and the two opposing sidewalls having a metal oxide thereon, exposing the substrate surface having the at least one feature thereon to a pre-cleaning process to form a cleaned metal surface (operation 220), and depositing a metal film on the cleaned metal surface (operation 230). In some embodiments, the metal film is deposited on the cleaned metal surface (operation 230) to fill at least one feature.

[0051] In some embodiments, the processing method 200 consists of: forming at least one feature that includes a top surface, a bottom surface, and two opposing sidewalls (operation 210), each of the top surface, the bottom surface, and the two opposing sidewalls having a metal oxide thereon, exposing the substrate surface having the at least one feature thereon to a pre-cleaning process to form a cleaned metal surface (operation 220), and depositing a metal film on the cleaned metal surface (operation 230). In some embodiments, the metal film is deposited on the cleaned metal surface (operation 230) to fill at least one feature.

[0052] Figures 3A to 3D A cross-sectional view of the Figure 2 processing method 200 shown in accordance with one or more embodiments of the present disclosure is shown. Figure 3A A cross-sectional view of a feature on a substrate is shown. Figure 3B Shown is Figure 3AA cross-sectional view of the feature shown in FIG. that has a clean metal surface after exposure to the unbiased cleaning plasma described herein. Figure 3C Shows a cross-sectional view of a metal film formed on the Figure 3B clean metal surface shown. Figure 3D Shows a cross-sectional view of a metal film filling the Figure 3B feature shown.

[0053] Referring first to Figure 3A , there is shown a substrate 300 having a surface such as a top surface 302 and at least one feature 350 formed thereon. For purposes of illustration, the drawings show a substrate 300 having a single feature 350; however, those skilled in the art will understand that there may be more than one feature 350.

[0054] The shape of the feature 350 can be any suitable shape, including but not limited to trenches and cylindrical through-holes. In this sense, the term "feature" means any intentional surface irregularity. Suitable examples of features include but are not limited to trenches having a top surface, two opposing sidewalls, and a bottom surface, peaks having a top extending upward from a surface (such as the substrate surface 302) and two sidewalls, and through-holes having sidewalls extending downward from a surface with a bottom. In some embodiments, the bottom of the through-hole includes an open bottom defined or bounded by an underlying material (e.g., a dielectric material), which may also define the two sidewalls, or the underlying material of the bottom may be a conductor such as a metal (e.g., copper), and the underlying material may be different materials. In one or more embodiments, at least one feature 350 includes one or more of a trench or a through-hole. In a particular embodiment, at least one feature 350 includes a trench. In more embodiments, the terms "at least one feature 350" and "trench 350" may be used interchangeably.

[0055] The trench 350 includes a top surface 325, a bottom surface 330, and two opposing sidewalls 320. The trench 350 has a depth to the bottom surface 330 and a width between the two opposing sidewalls 320. In some embodiments, the depth is in the range of 2 nanometers to 200 nanometers, 3 nanometers to 200 nanometers, 5 nanometers to 100 nanometers, 2 nanometers to 100 nanometers, or 50 nanometers to 100 nanometers. In some embodiments, the width is in the range of 10 nanometers to 100 nanometers, 10 nanometers to 20 nanometers, 10 nanometers to 50 nanometers, or 50 nanometers to 100 nanometers. In some embodiments, the aspect ratio (depth / width) of the trench 350 is in the range of 1:1 to 20:1, 3:1 to 20:1, 3:1 to 15:1, 5:1 to 20:1, 10:1 to 20:1, or 15:1 to 20:1.

[0056] The substrate 300 can be any suitable substrate material. In one or more embodiments, the substrate 300 includes a semiconductor material such as silicon (Si), carbon (C), germanium (Ge), silicon germanium (SiGe), gallium arsenide (GaAs), indium phosphate (InP), indium gallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), germanium (Ge), silicon germanium (SiGe), other semiconductor materials, or any combination of the foregoing. Although several examples of materials from which the substrate 300 can be made have been provided, any material that can serve as a basis for passive and active electronic components such as transistors, memories, capacitors, inductors, resistors, switches, integrated circuits, amplifiers, optoelectronic components, or any other electronic component can be utilized.

[0057] In some embodiments, the two opposing sidewalls 320 include any suitable dielectric material known to those skilled in the art. In some embodiments, the dielectric material includes a low-k dielectric material including, but not limited to, silicon oxide (SiO x ), silicon suboxide, silicon nitride (SiN x ), silicon nitride (Si 3 N 4 ), silicon oxynitride (SiO x N y ), or a combination thereof.

[0058] In some embodiments, the underlying material at the bottom surface 330 of the trench 350 can be a conductor such as a metal (e.g., copper), which can be the same or different from the sidewall material. In some embodiments, the bottom surface 330 includes the same material as the two opposing sidewalls 320.

[0059] Figure 3A A native oxide layer 360 (metal oxide layer 360) is shown, which is present on the top surface 325 of the trench 350, along the two opposing sidewalls 320, and on the bottom surface 330. Without being bound by theory, it is believed that due to etching the vias / trenches, an increased amount of metal oxide is formed on the bottom surface 330 compared to the top surface 325 or along the two opposing sidewalls 320. In some embodiments, the native oxide layer 360 includes molybdenum oxide (MoO x ), ruthenium oxide (RuO x ), or tungsten oxide (WO x ) or one or more of the foregoing. In some embodiments, the native oxide layer 360 is on top of the first metal film 370. In some embodiments, the first metal film 370 is conformally deposited directly on the top surface 325 along the two opposing sidewalls 320 and on the bottom surface 330. In some embodiments, the native oxide layer 360 is directly located on the first metal film 370.

[0060] The first metal film 370 may include any suitable metal known to those skilled in the art. In some embodiments, the first metal film 370 includes one or more of molybdenum (Mo), ruthenium (Ru), or tungsten (W).

[0061] Figure 3A The top surface 325, two opposing sidewalls 320, and bottom surface 330 are shown being exposed to an unbiased cleaning plasma 400 to remove the metal oxide layer 360, thereby forming a clean metal surface (as Figure 3B shown), the unbiased cleaning plasma consisting essentially of hydrogen (H 2 ) and oxygen (O 2 ) in a mixture in the range of 1% to 20% by molecules.

[0062] Separate remote plasmas and direct plasmas cannot effectively remove residues and native oxides (such as native oxide layer 360) within a structure (such as at least one feature 350). Remote plasma radicals cannot reach the structure trenches, such as at least one feature 350, sufficiently due to their lifetime, and direct plasmas cannot clean the sidewalls of the structure, such as two opposing sidewalls 320, due to directionality.

[0063] Current pre-cleaning processes involve exposing the substrate to a plasma of argon (Ar) and hydrogen (H 2 ) to remove native oxides. These pre-cleaning processes are performed in the presence of an external bias on the substrate surface, which may damage the dielectric and critical dimension (CD) / profile of the structure.

[0064] The inventors have surprisingly found that an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) can remove metal oxides from the substrate surface in the absence of an external bias on the substrate surface.

[0065] Advantageously, the unbiased cleaning plasma (shown by the cloud 400 in Figure 3A ) removes the metal oxide layer 360 from the top surface 325, two opposing sidewalls 320, and bottom surface 330 of at least one feature 350 without damaging the two opposing sidewalls 320 and / or the critical dimension (CD) / profile of at least one feature 350.

[0066] The unbiased cleaning plasma 400 advantageously removes all metal oxide layers 360 from the top surface 325, two opposing sidewalls 320, and the bottom surface 330. In some embodiments, the unbiased cleaning plasma 400 removes substantially all of the metal oxide layers 360 from the top surface 325, two opposing sidewalls 320, and the bottom surface 330. As used in this sense, "substantially all of the metal oxide layers 360" means that less than about 5%, including less than about 4%, less than about 3%, less than about 2%, less than about 1%, less than about 0.5%, and less than about 0.1% of the total composition of the metal oxide layers 360 remains on any surface of the trench 350 after exposing the top surface 325, two opposing sidewalls 320, and the bottom surface 330 to the unbiased cleaning plasma 400.

[0067] Figure 3B A cleaned metal surface 375 is shown, which is formed by exposing the top surface 325, two opposing sidewalls 320, and the bottom surface 330 to an unbiased cleaning plasma 400 to remove the metal oxide layers 360, the unbiased cleaning plasma 400 consisting essentially of hydrogen (H 2 ) and oxygen (O 2 ) in the range of 1% to 20% by molecules. When used in this way, the term "consisting essentially of" means that the unbiased cleaning plasma 400 contains greater than or equal to about 95%, 98%, 99%, or 99.9% of the said mixture. In some embodiments, the mixture of hydrogen (H 2 ) and oxygen (O 2 ) includes greater than or equal to 80% of hydrogen (H 2 ). In other embodiments, the mixture of hydrogen (H 2 ) and oxygen (O 2 ) includes greater than or equal to 90% of hydrogen (H 2 ). In some embodiments, the unbiased cleaning plasma 400 consists of a mixture of hydrogen (H 2 ) and oxygen (O 2 ) in the range of 1% to 20% by molecules. When used in this way, the term "consisting of" means that the unbiased cleaning plasma 400 excludes additional elements and / or components from the said mixture.

[0068] Figure 3C Shown at Figure 3BCross-sectional schematic view of a metal film (e.g., a second metal film 380) formed on a cleaned metal surface 375. In some embodiments, the first metal film 370 and the second metal film 380 have the same composition. In other embodiments, the first metal film 370 and the second metal film 380 are different. In some embodiments, the first metal film 370 and / or the second metal film 380 includes molybdenum (Mo), ruthenium (Ru), and / or tungsten (W) or an alloy of any of the foregoing. In some embodiments, the second metal film 380 is formed on the cleaned metal surface 375 by atomic layer deposition (ALD), chemical vapor deposition (CVD), or pulsed CVD (pCVD).

[0069] Other aspects of the present disclosure relate to a method that is part of a gap filling process. In some embodiments, the second metal film 380 is deposited on one or more high aspect ratio gap features, including vertical gap features and / or horizontal gap features, and the second metal film 380 in the gap features forms a horizontal interconnect through which current flows. Without being bound by theory, according to one or more embodiments of the methods described herein, gaps filled with a second metal film 380 conformally deposited on a cleaned metal surface 375 that has been exposed to an unbiased cleaning plasma 400 can improve the electrical operation of an integrated circuit by minimizing power loss and overheating in the integrated circuit.

[0070] See Figure 3D , the second metal film 380 is conformally deposited on the cleaned metal surface 375 to fill the feature 350. In some embodiments, the second metal film 380 is conformally deposited on the cleaned metal surface 375 by one or more of atomic layer deposition (ALD), chemical vapor deposition (CVD), or pulsed CVD (pCVD) to fill the feature 350 to a desired thickness.

[0071] In some embodiments, the second metal film 380 is laterally bounded by two opposing sidewalls 320 of the trench 350. As used in this context, "laterally bounded" means that the deposited material does not extend beyond the intersection between the top surface and the two opposing sidewalls 320. In some embodiments, the second metal film 380 extends over the trench 350. In some embodiments, the second metal film 380 fills the trench 350. As used in this context, a film that "fills the trench 350" has a volume that occupies at least 95%, at least 98%, or at least 99% of the volume of the trench 350. In some embodiments, the fill height of the second metal film that fills the trench 350 ranges from 30 nanometers to 75 nanometers, including within the range of 40 nanometers to 60 nanometers.

[0072] Embodiments of the present disclosure advantageously provide a metal film (e.g., the second metal film 380) that is free or substantially free of voids and seams. As used in this context, "substantially free" means that, on an atomic basis, less than about 5% of the total composition of the conformally deposited metal film (e.g., the second metal film 380) contains voids and / or seams, including less than about 4%, less than about 3%, less than about 2%, less than about 1%, less than about 0.5%, and less than about 0.1%.

[0073] The methods described herein can be performed in any suitable processing chamber known to those skilled in the art. The processing chamber can be a SiCoNi TM pre-cleaning chamber available from Applied Materials, Inc. of Santa Clara, California. The processing chamber can be a Selectra TM etching chamber available from Applied Materials, Inc. of Santa Clara, California. The methods described herein can be performed in, for example, an atomic layer deposition (ALD) processing chamber (including a spatial ALD processing chamber), a chemical vapor deposition (CVD) processing chamber, or a pulsed CVD (pCVD) processing chamber.

[0074] In some embodiments, the operations of the methods described herein are each performed in the same processing chamber or the same processing system. In some embodiments, the operations of the methods described herein are each performed in different processing chambers. In some embodiments, the different processing chambers are connected as part of a processing system. In some embodiments, the operations of the methods described herein are each performed in different processing chambers, and each different processing chamber is part of a separate processing system. In some embodiments, the operations of the methods described herein are performed without an intervening vacuum break.

[0075] In some embodiments, one or more operations of the methods described herein are performed in-situ without breaking vacuum. In some embodiments, one or more operations of the methods described herein are performed ex-situ. As used herein, the term "in-situ" refers to the operations of the methods described herein, each operation being performed in the same processing chamber or different processing chambers connected as part of a processing system, such that each operation of the methods described herein is performed without an intervening vacuum interruption. As used herein, the term "ex-situ" refers to the operations of the methods described herein, each operation being performed in the same processing chamber or different processing chambers, such that one or more of the operations of the methods described herein are performed with an intervening vacuum interruption.

[0076] One or more embodiments of the present disclosure are directed to a non-transitory computer-readable medium including instructions that, when executed by a controller of a processing chamber, cause the processing chamber to perform the methods described herein, such as methods 100 and 200. In some embodiments, the non-transitory computer-readable medium includes instructions that, when executed by a controller of a processing chamber, cause the processing chamber to: expose a substrate surface to an unbiased cleaning plasma comprising a mixture of hydrogen (H 2 ) and oxygen (O 2 ) to remove metal oxides and thereby form a clean metal surface, the unbiased cleaning plasma comprising oxygen (O 2 ) in the range of 1% to 20% by molecules. In some embodiments, the non-transitory computer-readable medium includes instructions that, when executed by a controller of a processing chamber, cause the processing chamber to: deposit a metal film on the clean metal surface.

[0077] In some embodiments, the non-transitory computer-readable medium includes instructions that, when executed by a controller of a processing chamber, cause the processing chamber to: expose a substrate surface having at least one feature to a pre-cleaning process, the at least one feature defining a trench having a top surface, a bottom surface, and two opposing sidewalls, each of the top surface, the bottom surface, and the two opposing sidewalls having metal oxides, the pre-cleaning process including exposing the top surface, the bottom surface, and the two opposing sidewalls to an unbiased cleaning plasma to remove metal oxides and thereby form a clean metal surface, the plasma consisting essentially of hydrogen (H 2 ) and oxygen (O 2) mixture composition. In some embodiments, the non-transitory computer-readable medium includes instructions that, when executed by a controller of a processing chamber, cause the processing chamber to: deposit a metal film on a cleaned metal surface. In some embodiments, the non-transitory computer-readable medium includes instructions that, when executed by a controller of a processing chamber, cause the processing chamber to: conformally deposit a metal film on a cleaned metal surface to fill a trench.

[0078] As used herein, "one embodiment", "certain embodiments", "one or more embodiments", or "an embodiment" refers to a particular feature, structure, material, or characteristic associated with an embodiment that is included at least in that embodiment of the present disclosure. Thus, appearances of phrases such as "in one or more embodiments", "in certain embodiments", "in one embodiment", or "in an embodiment" throughout this specification are not necessarily referring to the same embodiment of the present disclosure. In one or more embodiments, the particular features, structures, materials, or characteristics are combined in any suitable manner.

[0079] Although the present disclosure has been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatuses of the present disclosure without departing from the spirit and scope of the present disclosure. Accordingly, the present disclosure is intended to cover modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A method for removing metal oxide from a substrate surface, the method comprises: The substrate surface is exposed to a gas containing hydrogen (H 2 ) and oxygen (O 2 ) to remove the metal oxides to form a clean metal surface, wherein the unbiased cleaning plasma comprises oxygen (O 2 ).

2. The method according to claim 1, wherein the mixture of hydrogen (H 2 ) and oxygen (O 2 ) contains greater than or equal to 80% of hydrogen (H 2 ).

3. The method according to claim 1, wherein the mixture of hydrogen (H 2 ) and oxygen (O 2 ) contains greater than or equal to 90% of hydrogen (H 2 ).

4. The method according to claim 1, wherein the unbiased cleaning plasma removes substantially all of the metal oxide from the substrate surface.

5. The method according to claim 1, wherein the metal oxide comprises one or more of molybdenum oxide (MoO x ), ruthenium oxide (RuO x ), or tungsten oxide (WO x ).

6. The method according to claim 5, wherein the metal oxide comprises tungsten oxide (WO x ).

7. The method according to claim 1, wherein the unbiased cleaning plasma comprises one or more of inductively coupled plasma (ICP) or capacitively coupled plasma (CCP).

8. The method according to claim 1, wherein the substrate surface is maintained at a temperature in the range of 300 °C to 750 °C.

9. The method according to claim 1, wherein the method is performed at a pressure greater than or equal to 50 mTorr.

10. The method according to claim 1, the method further comprises: depositing a metal film on the cleaned metal surface.

11. A processing method, the processing method comprises: Expose a substrate surface having at least one feature to a pre-cleaning process, the at least one feature defining a through hole having a top surface, a bottom surface, and two opposing sidewalls, each of the top surface, the bottom surface, and the two opposing sidewalls having a metal oxide thereon, the pre-cleaning process comprising: exposing the top surface, the bottom surface, and the two opposing sidewalls to an unbiased cleaning plasma, the unbiased cleaning plasma consisting essentially of hydrogen (H 2 ) and oxygen (O 2 ) in a range of 1% to 20% by molecules to remove the metal oxide, thereby forming a clean metal surface.

12. The processing method according to claim 11, wherein the at least one feature has an aspect ratio in the range of 3:1 to 15:

1.

13. The processing method according to claim 11, wherein the mixture of hydrogen (H 2 ) and oxygen (O 2 ) contains hydrogen (H 2 ) of greater than or equal to 90%.

14. The processing method according to claim 11, wherein the unbiased cleaning plasma removes substantially all of the metal oxide from the top surface, the bottom surface, and the two opposing sidewalls.

15. The processing method according to claim 11, wherein the metal oxide comprises one or more of molybdenum oxide (MoO x ), ruthenium oxide (RuO x ), or tungsten oxide (WO x ).

16. The processing method according to claim 15, wherein the metal oxide comprises tungsten oxide (WO x ).

17. The processing method according to claim 11, wherein the unbiased cleaning plasma comprises one or more of inductively coupled plasma (ICP) or capacitively coupled plasma (CCP).

18. The processing method according to claim 11, wherein the substrate surface is maintained at a temperature in the range of 300 °C to 750 °C.

19. The processing method according to claim 11, wherein the method is performed at a pressure greater than or equal to 50 mTorr.

20. The processing method according to claim 11, the processing method further comprises: depositing a metal film on the cleaned metal surface.

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